a. A zooid having at some stages of ontogeny a protrusible lophophore, with or without the ability to feed. b. A common bryozoan containing feeding organs in the colony; capable of all life functions in a monomorphic colony.

Avicularium — The avicularium (pl. avicularia) in cheilostome bryozoans is a modified, non feeding zooid. The operculum, which normally closes the orifice when the zooids tentacles are retracted, has been modified to become a mandible. Strong muscles operate… … Wikipedia